Despite a substantial research literature on the influence of dimensions and exercises in assessment centers (ACs), the relative impact of these two sources of variance continues to raise uncertainties because of confounding. With confounded effects, it is not possible to establish the degree to which any one effect, including those related to exercises and dimensions, influences AC ratings. In the current study (N = 698) we used Bayesian generalizability theory to unconfound all of the possible effects contributing to variance in AC ratings. Our results show that ≤ 1.11% of the variance in AC ratings was directly attributable to behavioral dimensions, suggesting that dimension-related effects have no practical impact on the reliability of ACs.Even when taking aggregation level into consideration, effects related to general performance and exercises accounted for almost all of the reliable variance in AC ratings. The implications of these findings for recent dimension-and exercise-based perspectives on ACs are discussed. When, in the context of selection, appraisal, and development, behavioral criteria are used to evaluate individuals, it is essential that these criteria are measured reliably.Unsurprisingly, therefore, the measurement properties of assessment center (AC) ratings have come under close scrutiny in the applied psychology literature. In ACs, the behavior of jobholders or candidates is sampled across several work-related situations (exercises, e.g., a role play exercise, group discussion, presentation) and is typically assessed by trained assessors in terms of pre-defined behavioral dimensions (e.g., communication skills, teamwork, planning and organizing). As a result of their multifaceted measurement properties, incorporating dimensions, exercises, and assessors, ACs provide a rich source of information about the extent to which work-related behavioral criteria can be reliably measured in a job-relevant setting.Historically, researchers have questioned the extent to which behavioral dimensions are measured reliably in ACs, and have implied that researchers should utilize an exercise-oriented approach to scoring ACs